The uptake and binding of ellipticine was determined in viable human promyelocytic (HL-60) cells co-stained with Hoechst 33342 using a two-laser excitation flow cytometry system. Phase-sensitive FCM methods were used to measure the fluorescence lifetime of ellipticine bound within viable HL-60 cells. Ellipticine fluorescence lifetime was altered in both a time and dose dependent manner, demonstrating the disproportionate binding of ellipticine to DNA, to other cellular constituents. This study showed the utility of measuring the uptake and binding of chemotherapeutic agents in viable cell populations, and demonstrates the usefulness of fluorescence lifetime measurements. Fluorescence lifetime studies in progress are designed to compare drug uptake and binding in drug-resistant HL-60 cells and the wild-type cells.